High-power, high-performance switching amplifier for driving magnetic resonance imaging gradient coils

A high-power, high-efficiency switching amplifier capable of generating arbitrary gradient coil waveforms for a magnetic resonance imaging system is described. A high-frequency "partial-voltage" buck regulator feeds a "full-voltage" full-bridge inverter to relieve the full bridge of the necessity of switching when high voltage is needed by the load. When high voltage is needed, the partial-voltage buck circuit that employs faster lower voltage IGBT devices assumes the switching duty. When low voltage is needed, the high-voltage bridge inverter, operating from a low-voltage DC bus, assumes the switching duty. Since switching losses are approximately proportional to bridge input voltage, the switching losses incurred by the inverter are minimized.